Traditional laminate and parquet floors are usually installed floating on an existing subfloor. The joint edges of the floorboards are joined to form a floor surface, and the entire floor surface can move relative to the subfloor. As the floorboards shrink or swell in connection with the relative humidity RH varying during the year, the entire floor surface will change in shape.
Floating floors of this kind are usually joined by means of glued tongue and groove joints. In laying, the boards are brought together horizontally, a projecting tongue along the joint edge of one board being inserted into a tongue groove along the joint edge of an adjoining board. The tongue and groove joint positions and locks the floorboards vertically and the glue locks the boards horizontally. The same method is used on both long side and short side, and the boards are usually laid in parallel rows long side against long side and short side against short side.
In addition to such traditional floating floors, which are joined by means of glued tongue and groove joints, floorboards have been developed in recent years, which do not require the use of glue but which are instead joined mechanically by means of so-called mechanical locking systems. These systems comprise locking means, which lock the boards mechanically horizontally and vertically without glue. The vertical locking means are generally formed as a tongue, which cooperates with a tongue grove. The horizontal locking means comprising a locking element, which cooperates with a locking groove. The locking element could be formed on a strip extending from the lower part of the tongue groove or it could be formed on the tongue. The mechanical locking systems can be formed by machining the core of the board. Alternatively, parts of the locking system such as the tongue and/or the strip can be made of a separate material, which is integrated with the floorboard, i.e., already joined with the floorboard in connection with the manufacture thereof at the factory.
The floorboards can be joined mechanically by various combinations of angling, snapping-in, vertical change of position such as the so-called vertical folding and insertion along the joint edge. All of these installation methods, except vertical folding, require that one side of the floorboard, the long or short side, could be displaced in locked position. A lot of locking systems on the market are produced with a small play between the locking element and the locking grove in order to facilitate displacement. The intention is to produce floorboards, which are possible to displace, and which at the same time are connected to each other with a fit, which is as tight as possible. A very small displacement play of for instance 0.01-0.05 mm is often sufficient to reduce the friction between wood fibers considerably. According to The European Standard EN 13329 for laminate floorings joint openings between floorboards should be on an average ≦0.15 mm and the maximum level in a floor should be ≦0.20 mm. The aim of all producers of floating floors is to reduce the joint openings as much as possible. Some floors are even produced with a pre-tension where the strip with the locking element in locked position is bended backwards towards the sub floor and where the locking element and the locking groove press the panels tightly against each other. Such a floor is difficult to install.
Wooden and laminate floors are also joined by gluing or nailing to the subfloor. Such gluing/nailing counteracts movements due to moisture and keeps the floorboards joined. The movement of the floorboards occurs about a center in each floorboard. Swelling and shrinking can occur by merely the respective floorboards, and thus not the entire floor surface, changing in shape.
Floorboards that are joined by gluing/nailing to the subfloor do not require any locking systems at all. However, they can have traditional tongue and groove joints, which facilitate vertical positioning. They can also have mechanical locking systems, which lock and position the floorboards vertically and/or horizontally in connection with laying.